Effective complex dielectric constant of forest stand measured with GPS interferometer

In this paper, some results for the equivalent complex refractive index (ECRI) related to a forest stand are presented, as measured with the use of the global positioning systems (GPS). The real and imaginary parts of the ECRI were retrieved using the statistical averages of phase difference and logarithmic amplitude attenuation of the GPS signals. For this purpose the interferometer having two arms was developed. It was formed with three identical receivers located on a straight line, with the length of each arm being equal to 8 m. Two receives were placed in such a way as to avoid wave propagation through the forest canopy, while the wave path related to the third receiver crossed the forest canopy. Field measurements were carried out in a pine forest area near the city of Krasnoyarsk Russia, with the height, trunk thickness, and spacing of trees being of 10-15 m, 0,2-0,35 m, and 3-7 m, respectively. As a result, the equivalent refractive index and normalized attenuation coefficient concerning the forest stand were found to be of 0.00228plusmn0.00021 and 0.00183, respectively